2. Faults and Folds

14. Normal Fault In normal faulting, the hanging wall block moves down relative to the footwall block. The fault plane usually makes a high angle with the surface (> 45 degrees). Normal faults are associated with crustal tension.

19. Reverse Fault In reverse faulting, the hanging wall block moves up relative to the footwall block. The fault plane usually makes a low angle with the surface (< 45 degrees). Reverse faults are associated with crustal compression and are also known as thrust faults.

22. Strike-slip Fault In strike-slip faulting, the two blocks move either to the left or to the right relative to one another.

24. Joints have many important properties as planes of weakness in rock masses:

25. Joints and other discontinuities such as faults, cleavage, metamorphic foliation, and bedding planes control many important properties of rock masses including: Strength Compressibility Permeability

27. GEOLOGIC STRUCTURES Importance of geologic structures –Oil and natural gas are formed and found trapped in subsurface folds –Faults, joints, and fractures can act as a passageway for groundwater and host for valuable mineral deposits as ores of gold, silver and copper, etc. –Unconformities can be used to mark geologic time boundaries